Design And Research On Orthogonal Phase-Shifting Interferometry

Optical interferometry is widely applied to many fields,such as object surface roughness measurement,wavefront phase measurement and optical elements fabrication.It is a kind of significant approach in precision measurement.Phase shifting technique is employed to control the process of phase shifting in optical interferometry.When phase shifter is used to optical interferometer,the interferometer becomes a phase shifting interferometer.In the research process of interferometer,there are 3 factors which should be considered including anti-vibration,light weight design and fast data processing.It is important to research a phase shifting interferometer with 3 factors.In this thesis,an orthogonal phase shifting interferometry(OPSI)was proposed.And a fast data processing method was calculated by Jones matrix which is an expression method of polarizing optics.The data processing method was adopted to recover the wrapping phase distribution of samples.The phase distribution of a phase plate and liquid crystal optical phase array(LCOPA)were measured by OPSI.The main research contents are as follows:(1)The major error source is the phase shifter of OPSI.A high voltage drive power supply was employed to drive the phase shifter which was made of piezoelectric ceramics(PZT).A closed loop PZT shifter was employed,and it can reduce the error caused by vibration and nonlinear effect.It is essential to measure the relationship between driving voltage and phase.Two measurement methods were raised in this thesis.One method is based on interference fringe correlation coefficient.The other is based on four parameter sine wave curve fit.The phase shifter of OPSI was measured by these two methods to control the phase shifting.(2)Laser light quality is an important index of OPSI.A two grades laser expander lens with optical fiber was proposed in this thesis.It can get good laser light quality.And an opto-mechanical structure was designed for the lens and used for a part of OPSI.In the design processing of opto-mechanical structure for OPSI,the anti-vibration and light weight factors had to be considered.The natural frequency of structure is related to anti-vibration.The integrated structures of polarizing optical elements and conjugate optical system were evaluated by modal analysis for the optimization of structures.(3)The measurement experiment was based on OPSI.First,a piece of 25.4 mm diameter phase plate was employed in the measurement experiment.The data of OPSI was compared with WYKO which is a kind of commercial interferometer.The result shows that the peak to valley(PV)error maximum value of the phase distribution is 0.052?(?=1064nm)and the root means square(RMS)error maximum value is 0.006?.The error data meets the requirement of measurement.Next,the phase distribution of LCOPA was measured.The result presents that the PV value is 0.942?.The two dimensional phase distribution is identical with the far light field distribution of the diffraction spots.